On 29.01.2017 22:27, Julian Foad wrote:
Stefan, is this an edge case bug?
rep_read_contents() in libsvn_fs_fs/cached_data.c@1780363 is quoted below.
rep_read_contents() potentially reads one or more times from the fulltext cache
and then finds the fulltext cache is no longer available. I suppose this could
happen because the entry could be evicted because other entries are being more
recently/frequently accessed even though we haven't finished calling
rep_read_contents() for this particular rep.
In this case, rep_read_contents() calls skip_contents() to skip-read from the
window stream, to catch up that stream to the point we'd already reached in the
fulltext cache before it became unavailable.
Then we read the requested LEN bytes from the window stream, and update the
calculated checksum with those LEN bytes ... but not with the skipped bytes.
Won't that lead to a checksum mismatch when we reach the end of the rep?
Yes, that looks like a bug. I'll fix it next weekend.
The problem is not f7-specific and will only be transient
b/c the next reader will miss the cache and reconstruct
the content from the first window on.
Also, using bulk updates should reduce the incident rate
of this issue.
-- Stefan^2.
